Solid-State Image Device Stepped Contour Light Receiving Area
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Solution Overview
Problem
Conventional solid-state imaging devices are limited by the size of the semiconductor wafer, restricting the size of the light receiving section, which is insufficient for applications requiring larger imaging areas, such as dental X-ray systems with varying imaging modes.
Innovation Solution
The device features a light receiving section with a stepped contour shape, allowing for a larger area than a rectangular shape inscribed within a circular wafer, and includes a dummy photodiode region along the stepped edges to eliminate unnecessary carriers and reduce noise, ensuring uniformity and preventing signal delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If a rectangular light receiving section is produced from a circular semiconductor wafer, then the device can be manufactured using conventional processes, but the light receiving area is limited to the inscribed rectangle of the wafer
Solution Approach 1:
The light receiving section is divided into multiple regions with different contour shapes. The stepped contour design segments the traditional rectangular shape into stepped levels, allowing the device to utilize more of the circular wafer area while maintaining manufacturability through standardized fabrication processes
Solution Approach 2:
The invention transitions from a simple rectangular two-dimensional layout to a stepped contour design that effectively utilizes the circular wafer geometry. By adopting a stepped shape instead of a rectangular inscribed form, the light receiving area is expanded in the planar dimension while accommodating the circular wafer boundary
2Area of moving object
If the light receiving section is enlarged beyond the inscribed rectangle, then the imaging area increases, but noise from unnecessary carriers increases
Solution Approach 1:
The dummy photodiode region extracts and isolates the harmful effect of unnecessary carriers generated at the stepped contour edges. By providing a dedicated region that captures these carriers before they can enter the active light receiving section, the noise problem is separated from the main imaging area
Solution Approach 2:
The dummy photodiode region acts as an intermediary between the stepped contour structure and the active light receiving section. It mediates the harmful effect of edge-generated carriers by providing a transition zone that prevents these carriers from contaminating the imaging pixels
3Area of moving object
If a stepped contour shape is used to increase area, then the light receiving area expands, but uniformity of pixel characteristics deteriorates
Solution Approach 1:
The dummy photodiode region is strategically placed only at specific locations where the stepped contour creates potential uniformity issues. This local quality approach addresses the uniformity problem only where needed, rather than requiring global redesign of the entire light receiving section
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enables a larger light receiving area while maintaining uniformity and reducing noise and signal delay, making it suitable for applications like X-ray CT apparatuses.
Implementation Method 1
PPS type pixels including photodiodes each for generating charge of an amount according to an incident light intensity
Data Source
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AI summary
A solid-state imaging device of one embodiment includes a light receiving section including of a plurality of pixels 11 having respective photodiodes, the pixels being two-dimensionally arrayed in M rows and N columns; N readout lines disposed for the respective columns and connected with the photodiodes PD included in the pixels of a respective columns via readout switches; a signal output section for outputting a voltage value according to an amount of charge input through each of the readout lines; and a vertical shift register for controlling an opening and closing operation of the readout switch for each of the rows. A contour between one side along a row direction of the light receiving section and a pair of sides along a column direction has a stepped shape. A dummy photodiode region is formed along the stepped contour of the light receiving section.